In the present type of fixing device, curling is generated in various directions relative to a copy paper processing direction after copy paper transits a fixing device, this curling being caused both by differences in the heating conditions for the obverse and reverse sides of the copy paper and differences in the moisture evaporation loss due to the dissolution of the toner induced by the heating and pressure required to fix the toner to the copy paper. This curl causes paper jams when the copy paper is transported, as well as defects in paper condition when the copy paper is discharged to the receiving tray, thereby causing concern that unsatisfactory composite and duplex copies will be produced.
Conventional devices have a paper transport path from the heating roller which curves in the reverse direction to that in which the curl is produced so as to allow elimination of curling by drawing the copy paper through this curved portion of the paper transport path, thereby correcting the aforesaid curl and avoiding the resultant drawbacks (for example, Japanese Laid-Open patent Publication Sho 60-50547).
In the aforesaid conventional construction, however, resistance to or blockage of in-transit copy paper may occur when the paper transits the curved portion of the curved paper path, thereby raising concern that the paper will not transit smoothly.